Fertility and reproductive history in cancer patients, especially in long-term survivors of childhood cancer, and in men and women who reproduced during cancer therapy are studied for possible mutagenicity and teratogenicity of cancer treatments, and to discover hereditary patterns of cancer. Current phases include (1) interviews of 2,800 adults who survived cancer in childhood and their sibs as controls; (2) recall of National Cancer Institute patients for detailed examinations of offspring; and, (3) registry of pregnancies in young adult women through correspondence with physicians in Cancer and Acute Leukemia Group B.